Backpack



FIG. 1 is a perspective view of a backpack showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof; and,

FIG. 8 is a perspective view of the backpack shown in an alternative configuration.

The broken lines show portions of the backpack that form no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 